A medial approach for radial, ulnar, median and musculocutaneous nerve injection in calves.

Background: This study aimed to assess the feasibility of an ultrasound and nerve-stimulator-guided medial approach for a radial, ulnar, median and musculocutaneous (RUMM) nerve injection in calves.

Methods: After sedation with 0.2 mg/kg xylazine intramuscularly and 2 mg/kg ketamine intravenously (IV), seven calves were positioned in dorsal recumbency and a linear ultrasound probe was placed transversally on the medial aspect of the proximal third ohumerus. The radial (R) nerve was visualised adjacent to the deep brachial artery and the median and musculocutaneous (MM) and ulnar (U) nerves were visualised cranial and caudal to the brachial artery, respectively. A 20-gauge insulated needle was inserted in plane until near the R and MM nerves. Following a positive motor response (0.4‒0.6 mA stimulus), 0.15 mL/kg/site of tissue dye was injected in both forelimbs. The calves were then euthanased with 70 mg/kg pentobarbital IV. During dissection, staining was considered successful when more than 1 cm of the nerve was coloured in its whole circumference.

Results: The R, MM and U nerves were successfully stained in 13 (93%), 11 (79%) and six (43%) of the 14 injections, respectively.

Limitations: The spread of the dye might differ from that of local anaesthetics, so the findings should be interpreted cautiously.

Conclusion: A medial approach for RUMM nerve injection in calves seems feasible.